write_read_attr
status_t write_read_attr(BNode& node, read_flags flag);
write_read_attr(file, B_UNREAD);
write_read_attr(node, B_UNREAD);
write_read_attr(node, B_SEEN);
write_read_attr(node, read);
write_read_attr(node, flag);
return write_read_attr(node, flag);